Terpene-phenol resins are used in a variety of applications including adhesive and ink formulations and in the manufacture of engineering thermoplastics. Commercial terpene-phenol resins are typically produced by reacting a terpene with a phenol in a suitable solvent in the presence of a catalyst. After the reaction is substantially complete, the catalyst is deactivated with water or clay, and the resin is isolated from the reaction mass product by distillation to remove the solvent and by-products.
Terpene-phenol resins produced by currently available processes often have softening points above about 110.degree. C. and/or dark colors which reduce the usefulness of the product in certain adhesive and ink formulations.
Attempts to improve the color properties of such terpene-phenol resins have been largely unsuccessful in that they increase the production costs of these resins and/or reduce the product yield. For example, U.S. Pat. No. 3,383,362 to Gonzenbach describes a conventional method for making a phenol-terpene-cyclic polyolefin resin by reacting phenol or alkyl phenol, terpene or a low molecular weight propylene polymer and a cyclic polyolefin in the presence of a Friedel-Crafts catalyst and an aromatic, naphthenic or parraffinic hydrocarbon solvent. Products made by the process are said to have softening points ranging from 54.degree. to 123.degree. C.; however, the products exhibit an undesirable reddish brown color. Accordingly, for adhesive applications a color removal or color improvement step is often required. Furthermore, the cyclic polyolefins used to make the phenol-terpene-cyclic polyolefin compounds produce products having unacceptable amounts of low molecular weight fractions. The low molecular weight fractions tend to volatilize or cause "smoking" during preparation and use of hot melt adhesives containing the compounds.
It is therefore an object of the invention to provide a method for making relatively low softening point terpene-phenol-based resins having a relatively light color.
Another object of the invention is to provide a method for making terpene-phenol resins at a relatively low reaction temperature and in relatively high yield.
Still another object of the invention is to provide an improved method for making terpene-phenol resins having softening points in the range of from about 70.degree. to about 110.degree. C. without the need for a separate decoloration step.
A further object of the invention is to provide a method for making terpene-phenol compounds which exhibit improved thermal stability and therefore do not exhibit significant volatilization of low molecular weight fractions during production and/or use.